people have been predicting the pinball sky is falling, the bubble is about to pop, for as long as i've been in the hobby. hasn't happened yet and i doubt it will in the next decade. if anything, i see less short term flipping than i did a couple years ago (which is the real indicator of a potential bubble bursting). demand is solid, parts are available, interest is growing. the new games being built next year are a drop in the bucket compared to what's available, and even then those new games are really only an option for the high-end collector. they aren't going to saturate anything. worst case scenario, 90s DMD games take a minor hit (allowing more guys in their 30s to enter the hobby, being able to afford that WH20 or Addams Family or whatever they played as a kid).
on the subject of the economy, it's pretty much the same -- i can't remember a year in the last 25 where there hasn't been a contingent of people people armed with charts and graphs showing "proof" that the next great depression is right around the corner, and telling anyone who will listen to stock up on gold, canned goods, and ammo, and stuff all your money under the mattress. so far they are batting 1 for 25 (in 2007).